SN2-selective Grignard coupling with primary allylic diphenylphosphates was successfully achieved using Ni or Fe catalyst. In sharp contrast, a catalytic amount of CuCN· 2LiCl promoted a SN2′-selective coupling reaction. In the presence of the copper catalyst, stereochemically homogeneous γ-disubstituted allyl Grignard reagents reacted at the less substituted allylic terminus (α-position) with an allylic diphenylphosphate selectively ...
